Electric horn



April 7, 1953. R. c. NIELSEN ET AL, I 2,634,408

' ELECTRIC HORN Filed Jan. 14, 1949 4 Sheets-Sheet 1 Richard 0 MeATTORNEYS.

April 7, 1953 R. c. NIELSEN ETAL 2,634,403

ELECTRIC HORN Filed Jan. 14, 1949 I 4 Sheets-Sheet 2 FIG. 3 t .32

Richard 0. N'fii' Peter Nielsen a: I z QZ fig Q1 1 ATTORNEYS.

April 7, 1953 Filed Jan. 14, l

R. C. NIELSEN ETAL ELECTRIC HORN 4 Sheetg-Sheet 3 INVENTOR) Richard C.Nielsen Peter Nielsegz BY 4.]

ATTORNEYS.

April 7, 1953 R. c. NIELSEN ETAL 2,634,408

ELECTRIC HORN Filed Jan. 14, 1949 4 Sheets-Sheet 4 75:- I t I INVENTORS.

Richard C. Nielsen Peter .Nielsen Patented Apr. 7, 1953 UNITED STATESPATENT OFFICE ELECTRIC HORN Richard (J. Nielsen and Peter Nielsen,Omaha,

Nebr., assignors, by direct and mesne assignments, of one-half toJubilee Manufacturing Company, Omaha, Nebr., a corporation of Nebraska,and one-half to E. A. Laboratories, Inc., Brooklyn, N. Y., a corporationof New York Application January 14, 1949, Serial No. 71,013

16 Claims. 1 This invention relates to improvements in electricalwarning signals.

The primary object of this invention is the provision of an electricsounding signal of the vibrating diaphragm type wherein means isprovided to change the stroke of the signal diaphragm during sounding ofthe signal for the purpose of varying the sound pitch and volume.

A further object of this invention is the provision of an improvedelectric horn having a built in circuit maker and breaker which isnormally open: means being provided as a part of the horn structure toclose the circuit maker and-breaker, and to vary the sound of the hornduring the operation thereof.

A further object of this invention is the provision of an improvedelectromagnetic vibrating horn capable of producing an undistorted tonewhich may be varied as to pitch and volume during the sounding thereof.7

Other objects and advantages of this invention will be apparent duringthe course of the following detailed description.

In the accompanying drawings, forming a part of this specification, andwherein similar reference characters designate corresponding partsthroughout the several views,

Figure 1 is a side elevation of the improved horn,

Figure 2 is a plan view of the horn.

Figure 3 is a vertical cross sectional view taken substantially on theline 33 of Figure 2.

Figure 4 'is a fragmentary cross sectional view taken through the upperpart of the horn.

Figure 5 is an inside plan view of the part of the horn carrying theelectromagnet and circuit maker and breaker assemblage.

Figure 6 is a fragmentary cross sectional view of the upper part of thehorn, taken substantially onthe dot and dash line 6-6 of Figure 2 andshowing associated features of the operating linkage and diaphragmassemblage, including the electromagnet armature.

Figure '7 is a fragmentary sectional view showing other details of thehorn structure.-

Figure 8 is a wiring diagram of the circuit maker and breaker assemblageof the horn structure showing the contacts open, the control linkagebeing shown in dot and dash lines.

Figure 9 is a diagrammatic view of the parts shown in Figure 8, but withthe control linkage imposition to close the circuit maker and breakercontacts for the purpose of setting the signal in operation.

Figure 10 is another diagrammatic view of the parts shown in Figures 8and 9. but with the diaphragm in position which it will assume uponattraction of its armature by the electromagnet for the purpose ofbreaking the magnetic coil circuit.

In the drawings, wherein for the purpose of illustration is shown only apreferred embodiment of the invention, the letter A may generallydesignate the electric warning signal or horn. It includes a casing orframe structure B; electromagnet C: diaphragm and armature assemblage D:circuit maker and breaker assembla e E, and control linkage F.

The casing structure B includes the portions H] and I I which arerespectively annularly flanged at l2 and Him receiving between the outerperipheral portion of the diaphragm l5 constituting part of theassemblage D. The flanges l2 and I3 may be connected by rivets it, ordetachably connected by bolts if so desired. The casing portion Hincludes the bell mouth 18. The casing portion it houses and supportsthe electromagnet C; the circuit maker and breaker assemblage E, and thecontrol linkage F. To that end it includes the outer cupshaped portion20 defining a compartment 2! therein to receive the-electromagnet C. Theportion 20 is provided with an annular flange 23 paralleling the topwall 24 of the casing portion 20, and an annular wall portion 25connects the flanges l2 and 23. v

The electromagnet structure C includes the U-shaped steel pole piece3B-, core 3! and coil 32. These parts are mounted detachably by nut andbolt means 33 upon the top wall 24 of the casing portion 10, with thecore 3| extending from the coil within the compartment 2! of the casingportion Ill, as shown inthe drawings, between the arms of the pole piece30.

One end'of thecoil 32 is connected to a live terminal 40- mounted on thecasing, as shown in Figure 4; the terminal 403 being insulated at ll(see Figure 4), from the casing structure B, which of course is groundedin a circuit, usually the chassis frame of the automotive vehicle towhich the signal is attached. The other end of the coil 32 is connectedin circuit to a terminal screw 44, shown-in Figures 5 and 6 which is incircuit with a leaf spring type contact arm #15 forming part of thecircuitmaker and breaker assemblage E. The leaf spring arm is mounted ininsulated relation upon casing l 0 by means of the terminal screw. 44-and-another screw 45 mounted upon the casing wall, 23. The spring armstructure 45 extendstransv'ersely across the compartment in the casingportion so, as shown in Figures 5 and 6, and is adapted to carry both 3coil and resistor contacts 10 and I to be subsequently described.

The diaphragm and armature assemblage D preferably comprises theflexible sheet metal diaphragm l5 .of-sumcient .springiness toinherently v assume a predetermined position; the peripheral marginsthereof being clamped between the flanges of the casing portion it andH, as indicated in the various views of the drawings. As will be notedfrom Figure 3, the armature is attached centrally to the diaphragm l5and includes the rectangular-shaped portion "52 clamped by means of adetachable .bolt assemblage .51., of head portion 50 of which faces thecore. The armature portion 52 is provided with .a pair of outstandingright angled studs or prongs .53 :at diametrically opposed sides of theelectromagnetcore 3| for cooperation with the "springarm portions 51 and58 of a leaf spring yoke The latter is secured at El to the wall portion23 of thecasing within the electromagnet compartment of the casingstructure 10. The yo'ke has arms 5'! and 58 in straddling relation withthe electromagnet core 31, as will be noted from the various views .ofthe drawings, .and particularly Figure .5, and in which view in dot anddash lines designate the relative positions of the armature studs orprongs 53. V

The leaf spring contact arm intermediate its ends .is provided with the.coil contact point 10 located in a plane intersecting the .central.axis .of the leaf spring yoke 560,; the latter at the juncture of thespring arms 51 and 58 supporting a complementary contact point Hgtherelation .of these parts being .best illustrated in Figures '6 and '7.

The control linkage 2F is provided for the pur- ,pose .of closing anormally open circuit through .the electromagnet coil structure. To thatend it includes a connecting rod or plunger 80 reciprocably supportedupon the end wall 24 of the casing structure L0 in right angled relationtherewith; its inner .endfbeing .detachably and securely clamped ininsulated relation upon the leaf spring arm 45., intermediate the ends.of the latter, as shown in Figure 13 of the drawings. compression.spring 85 is situated between "the leaf .-spring 45 and .the under sideof the wall .213 of the casing normally urges .theleaf spring '45 intothe position shown in Figure 6. An operating lever 88 is pivoted at .89upon abracketstructure secured upon the outer surface of the casing wall.24.; .a cam end thereof extending beneath the end washer 9] upon theconnectiing rod or plunger .80. The spring 85 is under compression inthe relation of parts shown in Figure 6 with the cam end of the lowerarm portion of the .bell crank operating lever 08 clamped between thetop surface of the wall .24 and the under surface of the washer 9| "tohold the .circuit contacts open.

.A resistor element I00 is located upon the in- .side surface of theWall .23; one end of "it being secured upon .the casing structure byrivet 10!. Its opposite end is secured to a terminal bolt I 05 mountedin insulated relation upon the casing wall 23 as shown in Figure 3. Thisterminal 105' provides a contact point for complementary cooperationwith a contact point I06 secured upon the extreme outer end of the leafspring "type .contact arm 45.

"While the wiring in diagrams shown in Figures the line; terminal 40 ofthe (casing structure, this being indicated "by the line H2 in Figures8, 9 and 10 of the drawings. In the wiring diagrams the referencecharacters applied to th various parts of the warning signal are thesame as those above designated. With the control linkage in the .offposition shown in Figure 8, the coil contact points 10 and TI are spacedas are also the resistor contact points I05 and I06. Moving the :bellcrank .lever 88 against the resistance of the spring will pull the arm45 to engage the coil contacts 1.0 :and .11. The coil 32 becomesenergized and attracts the armature 52. The studs 53 which engage theleaf spring yoke 60 upon whiehthe coil contact point TI is mounted movesthe yoke away from the contact point supporting arm 45.. This separatesthe contact points wand H and the circuit is broken through the coil.This position is shown in Figure 1.0 of the V drawings. The diaphragm1.5 now being under spring tension will move, .as soon :as the circuitis broken, from the position shown in Figure 1.0 to normal position. Theprongs 53 move therewith and permit the spring'yoke arm .60 to move, dueto its inherent springiness-so that its terminal point Hwill-.again-engage the terminal point 10 foragain closing the-circuitthrough the .coil, and thus the cycle continues; the .dia-' phragmvibrating and setting an :air column in .action.

The resistor circuit is provided Jtor "the protection of the coilcontact points .10 and 2H inrorder to reduce :flash .as the contact,points 1 0 and ELI,

.openand close, The coil contact points 1 0 and 1| are set .to closejust slightly .ahead of the resistor contact points I05 and H16. Whenthe coil contacts 10 and ll open .at the limit (of instroke of thearmature, as shown in Figure-.10., it is'to be noted that the resistorcontacts :l05 and 1.06 .are engaged. Thus a current is flowing throughthe magnet coil even though the coil contacts 10 and H are separated.The force .of this current, however, is small, since it is -.control-ledby theresistor unit 100, and this :does not interfere with diaphragmaction.

Referring to improved features in pperation of the warning signal, it.is to :be noted that all switch .contact points *withinthecasingstructure are ."normally .open. This :is "in .contradlsti-n'ction to.other horn structures 'whose :breaker points are .normallyclosed. It isnot necessaryto provide a push button control for :the :horn icir--cuit; conventional push button structure I'fOl' ordinary hornsinormall-y keeping the electric .cir-

present invention has the advantage of economy and simplicity, becauseit eliminates separate push button electrical control elements with allof their attendant wires, terminals, relay structure, etc. 7

.In the "improved warning signal the control linkage enables thefrequency vibration 'of the diaphragm assemblage to be changed duringsounding of the horn This is accomp'lishedi-by changing the relativeposition of the breaker points 10 and TI through the control linkage.Holding "the control linkage in predetermined position during soundingof the 'horn spaces the contact points of the circuit for the coil in apredeterminedrelation so that there will be 'a constant stroke of thevibrating diaphragm and the volume and pitch of tone of the horn willremain constant. However, if the control linkage is now moved so as tofarther space the contact point of the spring arm structure 45 from theplane of the diaphragm, such will also move the contact point 1| fartheraway from the diaphragm depends on the position in which the operatorplaces the control linkage. Since the lever of the control linkage canbe moved either Way while the horn is blowing, the sound produced can bevaried during blowing of the horn to suit the operator's pleasure. It isobvious that the volume and pitch depend upon the length of stroke ofthe diaphragm, and such variation produces an undistorted tone which ispleasant, distinctive, etc.

It is important to note that the means for moving the coil terminals.etc. insures a pure undistorted tone, because the breaker points openand close in a plane intersecting the center of the diaphragm: theelectromagnet thus being enabled to pull the diaphragm assemblagestraight to the magnet and to permit its release in a plane normal tothe axis of the coil. There is no buckle and weaving during vibration ofthe diaphragm and this tends to produce a clear and vention herein.shown and described without departing from thespirit of the invention orthe scope of the following claims.

We claim: 1. In an electric sounding signal the combination of acasing,-a sound producing vibrator carried by the casing, anelectromagnet carried by the-casing: having a coil, an armature for thevmagnet carried :by said vibrator, an electric circuitv for 'theelectromagnet including a circuit maker and breakercarried bythe'casing, and means for directing a minor current through theelectromagnet coil just prior to and during opening of the circuit makerand breaker.

2. In an electric hornthe combination of a casing, a vibrating diaphragmcarried by the casing structure, an electromagnet including a coilcarried by the casing, an armature for the electromagnet carried by saiddiaphragm, a circuit maker and breaker carried by the casing including apair of spring arms having normally disengaged contact points thereon, acircuit connected with said'spring arm contact points for said coil,means'for moving said contact points into closing relation, meansoperated by the diaphragm and zarmature for moving one of the springarmsto a circuit opening position immediately after closingof thecircuit by said contacts, andmeans for selectively varying the positionof'the spring arm upon which the other contact point is mounted so as tovary the effective opening and closing relation of the circuit by saidcontact points with respect to the normal position of the diaphragminorderto control the freouencystroke of said diaphragm.

traction by said electromagnet.

3. In an electric horn construction the com-" bination of a casing, avibrating diaphragmv caried by the casing having an armatureconnectedtherewith, an electromagnet carried by the casing including acoil in operating relation with-respect to said armature, a circuit forthe coil, a circuit maker and breaker including individual yieldablemembers mounted upon the casing having individual normally disengagedcontact points thereon for said circuit, means carried by the casing forclosing said contact points, said last mentioned means operating to movesaid individual members to vary the position of said contact points withrespect to the rest position of said diaphragm in a line normal to theplane of the diaphragm, and means associated with said diaphragm andarmature for moving one of said members and its contact point awayfromthe contact point of the other member to disengage said points andopen the circuit upon extended movement of the armature as an incidentof at:

4. In an electric horn structure the combina tion of a casing, adiaphragm mounted in the casing structure, an electromagnet carriedbythe casing, an armature for the electromagnet carried by the diaphragm,a resilient circuit mak, ing and breaking arm carried by the casing, asecond resilient circuit making and breaking arm carried by the casing,a circuit for said coil, normally spaced contact points for the circuitcarried by said arms, operating means to engage the points and close thecircuit,,- and means operated by the armature and diaphragm for movingone of said arms to necessitate disengagement of the contact points atextended positioning of the armature and diaphragm as an incident ofattraction by said electromagnet. y 5. In an electric horn-structure thecombination of a casing, a diaphragm for-the casing structure, anelectromagnet carried by the easing, an armature for the electromagnetcarried by the diaphragm, a resilient circuit makingand breaking armcarried by the casing, a second resilient circuit making and breakingarmqcarried by the casing, a circuit for said coil, normally spacedcontact points for thecircuit carried by said arms, operating means toengage the points and close. the circuit, means operated -by. movementof the armature and ,diaphragm'for moving one of said arms to disengagethe contact points at extended positioning of the armature and diaphragmas an incident of attraction by said'electromagnet, and means formovingsaid arms and varying the position of said contacts toward and away fromthe plane of operation of bination of a casing, avibratingdiaphragm-carried by the casing structure, an electromagnetcarried by the casing including a coil, an armature for theelectromagnet carried by said diaphragm, a resilient circuit making andbreaking arm carried by the casing inherently assuming a predeterminedposition and having a contact point thereon, means for moving said am tochange the relative position of thecontact point thereof within saidcasing in a line normal to the operating planeof the diaphragm, a secondresilient arm carried by the casing inherently assuming a predeterminedposition and"-having a contact point connected therewith infnormaldisengaged relation with respect tothe contact point of the firstmentioned contact arm, a coil circuit for said contact points,saidsecondcom 7 V #tantarm bearing'such a relation "to the gfirst men--tloned contact arm that it will also be moved :by andwith controlledmovement of the first mentioned contact arm, tandmeans operated bymovement of the diaphragm and its armature .for moving the second armand its contact point .to break a circuit immediately after energizationof the cl-ectromagnet.

' In an electric sounding signal the combination of a frame, anelectromagnetic assembly upon said frame, a diaphragm mounted upon saidframe having an armature connected therewith for said electromagneticassembly, a spring arm mountedzupon said frame inherently assuming apredetermined position and having .an electric contact mounted thereonand movable therewith, a second spring arm :mounted upon said Birameinherently assuming .a predetermined position and having an electriccontact mounted thereon and movable therewith, said contacts providing a:norma'lly opened circuit maker and breaker, a circuit :for' saidelectromagnet having said contaots opera'tively connected therein,operating means mounted upon the frame and connected with the first ofsaid spring arms to move the :same and cause engagement of said contactsclosing of the circuit thruthe electromagnet, and means mounted upon thediaphragm and movable therewith to engage the second spring arm when thediaphragm is in extended position immediately after closing of thecircuit to cause movement of said second arm and -.disengagement of saidcontacts and resultant opening :of the circuit.

158'. In an electric sounding signal the-com'binai a mounted upon theframe andconnected with the 'iirst of said spring arms to move the sameand cause engagement of saidcontacts and closing 01' a "circuit 'thru'the .eleetromagnet, means mounted upon 'the diaphrag'm and movablethere'- with-to engage the second spring arm when the diaphragm isinextended position to causem'ovement of said second arm and disengagementof said contacts and opening of the circuit, said operating means havinga controlled range of movement to enable the engaged contacts tobeselectively moved towards and away from the normal rest position of thediaphragm during vibration of the diaphragm whereby said diaphragm maybe required to travel predetermined varied distances in order to effectdisengagement oisaid' contacts and thereby selectively controliling thelength of travel of the vibrating diaphragm and the sound pitch causedthereby. 7

In :an electromagnetic horn, a, frame; an

"electromagnet mounted 'upon said frame, a (11- 'iaphragm :mounteduponsai'd frame for said elec- -'Etromagnet,' a circuit for saidelectromagnet including a circuit fma'k'er and breaker, control meansfor operating said circuit maker and "breaker, and means operated by thecontrol means to wary the sonndeffective pitch s31 diaphragmsimultaneously with circuit closing operation of said circuit maker andbreaker;

.10. In an electromagnetic horn, a trams, an el'ectromagnet mounted uponsaid :frame, a diaphragm mounted upon said frame zfor saidelectromagnet, .a spring arm mounted upon said frame having a contactthereon, aseoond spring arm mounted upon said frame having a contactthereon circuit making and breaking relation with respect to the contactof the Lfirstmentioned spring arm, opera-ting mean mounted upon saidframe, said arms being so related in their normal position that theircontacts are out of relative engagement, means normally :maintaining theoperating means such position that the contacts will :be out of relativeengagement, a circuit having said contacts therein and having "theelectromagnet operatively connected therein, said operating means havingconnection with one of said Spring arms to enable dt-ito moved-and.thereby to, engage said contacts for closing said circuit and :fiex'ingthe second sprin arm for relatively :ohangingthe "position of :bothw'fsaid contacts with respect to the normal plane :of operation of thediaphragm, and means carried by the diaphragm for engaging the springarm "free 01' direct connection with the control means for causing it tomove at .extende'dpositioning of the diaphragmior disengaging contacts.

ill. -An electrically actuated horn having :an intermittentlyenergizable solenoid attracting a diaphragm carrying armature includingin combination a .reciprocable :m'ovahle strip electrically connected toone terminal of said solenoid, a first contact enga'geable with'saidreciprocabl'e strip to energize said solenoid, a :mem'ber supportingsaid first contact :mounted between :sazidsolenoifi and armature so asto 'be vibrated by said armature "and vary the position of engagement"be tween said "first contact and said ireciprocaible strip, a secondcontact 'engageable with said reciprocable strip to energize saidsolenoid at -.c more extreme position of reciprocation v:oisald stripthan said engagement between said first contact and said strip, aresistance connected between said first and said second oontactsiso thatsaidxzsolenoid is energized iby engagemerit between said second contactand said reciproc'a'ble strip through isaid resistance and means forreciprocating said reciprocable strip.

12..In :a horn having an JmtermittBntly'energizable solenoid attractinga diaphragm carrying armature and :a spring vzllrxed by said tarma--ture upon attraction by :said'soienoidrthe combination of 1a firstcontact :on said spring, :a movable arm disposed adjacent and'atransrerse to said spring and electrically :connectedto one terminalof :said solenoid, [one end of said "am immovable, one end of said arm:movable in :a direction toward and away from said spring, "are'ciprocable member 'coop'erable and movable with the movable end ofsaid "movable arm, mechanical means coopera'ble with said reciprocablemember to variably operate said'member in the direction of themovementof :said arm. a second contact on said arm out of contact "with saidfirst contact inthe tie-energized sta'te of said solenoid and:engagea'ble with :said first contact to energize said solenoid, saidreciprocation of saidmovable arm being variable to vary the position ofengagement between said firstand second contacts along the direction ofthe movement of said movable arm whereby actuation of saidmechanicalzmean'scauses reciprocation of said reciprocable member andsaid movable arm to bring about a variation in the engagement betweensaid first and second contacts and the fiexure of said spring by saidarmature with a consequent variation in the sound produced by saiddiaphragm.

13. In a horn having an intermittently energizable solenoid attracting adiaphragm carrying armature and a member engaged by said armature uponattraction by said solenoid the combination of a first contact on saidmember electrically connected in the solenoid energization circuit, afirst reciprocable means adjacent said member electrically connected insaid solenoid energization circuit and movable in a direction toward andaway from said member, a second means variably operable in the directionof reciprocation of said first means, said second means being cooperableand movable with said first reciprocable means, a second contactattached to said first reciprocable means and out of contact with saidfirst contact in the de-energized state of said solenoid, said firstreciprocable means and said second contact being movable to engage saidsecond contact with said first contact to energize said solenoid, saidreciprocation of said reciprocable means being variable to vary theposition of engagement between said first and second contacts along thedirection of the movement of said first reciprocable means wherebyactuation of said second means causes reciprocation of said firstreciprocable means to bring about a variation in the engagement betweensaid first and second contacts and the movement of said member by saidarmature with a consequent variation in the sound produced by saiddiaphragm.

14. In a horn having an intermittently energizable solenoid attracting adiaphragm carrying armature the combination of a spring flexed by saidarmature upon attraction by said solenoid, a first contact on saidspring movable therewith and connected in the solenoid energizationcircuit, a reciprocable arm independent of and disposed adjacent to saidspring and electrically connected to one terminal of said solenoid, oneend of said reciprocable arm immovable, the other end of saidreciprocable arm being freely movable in a direction toward and awayfrom said spring, reciprocable means cooperable with said free end ofsaid reciprocable arm to variably reciprocate said reciprocable armtoward and away from said spring, a second contact on said reciprocablearm out of engagement with said first contact in the de-energized stateof said solenoid and engageable with said first contact to energize saidsolenoid, said operation of said reciprocable means being variable tovary the position of engagement between said first and second contactsalong the direction of the reciprocation of said reciprocable armwhereby actuation of said reciprocable means causes reciprocation ofsaid reciprocable arm to bring about a variation in the engagementbetween said first and second contacts and the fiexure of said spring bysaid armature with a consequent variation in the sound produced by saiddiaphragm.

15. In a horn having an intermittently energizable solenoid attracting adiaphragm carrying armature the combination of a spring interposedbetween said armature and solenoid, a free end of said interposed springextending transversely halfway across said armature and anchored at theopposite end so as to be flexed by movement of said armature toward saidsolenoid, a first contact positioned on said spring.

substantially equidistant between said anchored end and said free endand electrically connected to one terminal of said solenoid, a movablearm disposed adjacent to said spring and electrically connected to oneterminal of said solenoid, a fixed end of said movable arm, a freelymovable end of said movable arm reciprocable in a direction toward andaway from said spring, a reciprocable member cooperable and movable withthe movable end of said movable arm, means cooperable with saidreciprocable member to variably operate said member in the direction ofthe reciprocation of said movable arm, a second contact on said arm outof contact with said first contact in the de-energized state of saidsolenoid and engageable with said first contact to energize saidsolenoid, said reciprocation of said movable arm being variable to varythe position of engagement between said first and second contacts alongthe direction of the reciprocation of said movable arm whereby actuationof said means causes reciprocation of said reciprocable member and saidmovable arm to bring about a variation in the engagement between saidfirst and second contacts and the fiexure of said spring by saidarmature with a consequent variation in the sound produced by saiddiaphragm.

16. In an electromagnetic horn the combination of a frame, anelectromagnet mounted upon said frame including a coil, a diaphragmmounted upon said frame in position for attraction by saidelectromagnet, a normally open circuit maker and breaker mounted uponsaid frame for closing of a circuit through the coil of saidelectromagnet, means carried by the diaphragm for opening the circuitmaker and breaker after circuit closing during vibration of thediaphragm, and operating means for closing the circuit maker and breakerfor energizing the electromagnet including means to vary the distance ofcircuit breaking operating of said circuit maker and breaker withrespect to the diaphragm to vary the sound efiective pitch of thediaphragm during horn operation.

RICHARD C. NIELSEN. PETER NIELSEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,729,284 Dorsey Sept. 24, 19291,759,443 Dorsey May 20, 1930 2,011,957 Vasold Aug. 20, 1935 2,094,772Critchfield Oct. 5. 1937 2,450,933 Bell Oct. 12, 1948

